JP2018035924A - Vacuum heat insulation panel for electrical equipment - Google Patents

Abstract

An object of the present invention is to maintain, over a long period of time, good thermal insulation performance close to the thermal insulation performance immediately after manufacture by suppressing an increase in thermal conductivity within a certain period of time immediately after manufacture of a vacuum thermal insulation panel. A method for manufacturing a vacuum insulation panel in which a core material 1 made of inorganic fibers is wrapped in an outer wrapping material 2 made of a stainless steel plate, and an inner space 3 of the outer wrapping material 2 wrapping the core material 1 is evacuated. The moisture content of the core material 1 is 0.05% by weight or less, the surface roughness Ra of the surface facing the internal space of the outer wrapping material 2 is 0.2 μm or less, and the inside of the outer wrapping material 2 The peripheral portion of the outer wrapping material 2 is sealed by welding while the pressure in the space 3 is set to 1 Pa or less. [Selection drawing] Fig. 1

Description

  The present invention relates to a vacuum heat insulating panel used in, for example, a beverage vending machine, a heat exchanger such as a refrigerator and a hot water supply device, and an electric device such as an electric pot and a copy machine.

  In recent years, energy saving is desired because of the importance of suppressing global warming, which is a global environmental problem, and energy saving measures for various facilities are being promoted. For beverage vending machines, refrigerators, automobile cooling containers, heat exchangers such as hot water supply equipment, and heat insulation equipment such as electric pots, in order to reduce the amount of electricity consumed, the heat insulation performance of the internal space is increased, Attempts have also been made to improve the heat shielding performance that blocks heat entering from the outside.

  Patent Document 1 discloses that a vacuum heat insulation panel is used as means for improving heat insulation performance.

  The vacuum heat insulation panel disclosed in Patent Document 1 stores a core material made of inorganic fibers in a case made of a gas barrier film together with a gas adsorbent, vacuum-sucks the inside of the case, and opens the opening with a film heat seal. It is manufactured by sealing.

JP 2004-308691 A

  In the vacuum heat insulation panel disclosed in Patent Document 1, since heat sealing is adopted as a method for sealing the opening, moisture is transmitted from the sealing portion, the degree of vacuum is reduced, and the thermal conductivity is reduced. There is a problem of rising. In particular, vending machines or the like have many opportunities to come into contact with moisture for a long period of time due to the outdoor environment, and the surroundings of the vacuum heat insulation panel become a humid environment, and moisture permeation increases. Therefore, the degree of vacuum decreases with the passage of time.

  In addition, since the gas adsorbent is sealed together with the core material in the outer packaging material, the moisture that permeates from the sealing portion and enters the inside is adsorbed by the gas adsorbent, so that the degree of vacuum decreases for a certain period of time. Although the amount of adsorption of the gas adsorbent is limited, after a certain period of time, the degree of vacuum decreases and the thermal conductivity increases.

  The present invention was devised in view of such circumstances, and immediately after the manufacture of the vacuum heat insulation panel, by suppressing the increase in the thermal conductivity within a certain period, the good heat insulation performance close to the heat insulation performance immediately after the manufacture. An object of the present invention is to provide a vacuum thermal insulation panel capable of maintaining the temperature for a long time.

  The vacuum heat insulation panel of the present invention is a vacuum heat insulation panel in which a core material made of an inorganic fiber is wrapped in an outer packaging material made of stainless steel plate, and the inner space of the outer packaging material that wraps the core material is in a vacuum state, Heating the material, the moisture content of the core material is 0.05 wt% or less, the surface roughness Ra of the surface on the inner space side of the outer packaging material is 0.2 μm or less, the core material The outer wrapping material is wrapped, and the peripheral portion of the outer wrapping material is sealed by welding in a state where the pressure of the inner space of the outer wrapping material wrapping the core material is 1 Pa or less.

  Since the performance deterioration of the vacuum heat insulation panel of the present invention is performed by sealing the outer packaging material by welding, moisture permeation can be suppressed, and the change with time can also be suppressed.

  The manufacture of the vacuum heat insulation panel of the present invention is to produce a vacuum heat insulation panel in which a core material made of inorganic fibers is wrapped in an outer packaging material made of stainless steel plate, and the inner space of the outer packaging material that wraps the core material is in a vacuum state. On the assumption that the core material is heated to a moisture content of 0.05% by weight or less, the core material is wrapped with the outer packaging material, and the outer packaging is wrapped with the core material. This can be carried out by a method of a sealing process in which the opening of the outer packaging material is sealed by welding in a state where the pressure in the internal space of the material is 1 Pa or less.

  According to the vacuum heat insulation panel concerning the present invention, possibility that the good heat insulation performance near the heat insulation performance immediately after manufacture can be maintained over a long period increases.

It is an exploded view of a vacuum heat insulation panel. It is a figure which shows the outline of the manufacturing process of a vacuum heat insulation panel. It is a graph which shows the time-dependent change of the heat conductivity of the vacuum heat insulation panel which each uses the several core material from which the moisture content to contain differs.

  Hereinafter, embodiments of the vacuum heat insulation panel will be described. For example, as shown in FIG. 1, the vacuum heat insulation panel manufactured by the manufacturing method according to this embodiment wraps a core material 1 with an outer packaging material 2 made of a stainless steel plate, and the inside of the outer packaging material 2 that wraps the core material 1. The space 3 is in a vacuum state.

  The core material 1 supports the outer packaging material 2 from the inside so that the outer packaging material 2 of the manufactured vacuum heat insulation panel 10 is not crushed by atmospheric pressure. An inorganic fiber is used for the core material 1. Examples of the inorganic fiber include glass wool and ceramic fiber. It is desirable to use a core material that does not contain any binder. This is because if a core material containing a binder is used, outgas is generated from the core material over time, and the heat insulation performance may deteriorate over time.

The outer packaging material 2 is composed of two outer packaging plates 2A and 2B. Stainless steel sheets are used for the outer cover plates 2A and 2B. The two outer packaging plates 2A and 2B have the same shape and size at the peripheral edge. A bulging portion 4 is formed on at least one outer packaging plate 2B, and the peripheral sides of the two outer packaging plates 2A and 2B are aligned and overlapped to form a concave side surface of the bulging portion 4 of one outer packaging plate 2B. An internal space 3 is formed between the other outer packaging plate 2A. The surface roughness Ra of the outer cover plate surface inside the inner space 3 constituted by the outer cover plates 2A and 2B is 0.2 μm or less, and the core material 1 is accommodated in the internal space 3. The two outer cover plates 2A and 2B illustrated in the drawings are rectangular when viewed from the thickness direction.
The surface roughness Ra of the surface on the inner space 3 side of the outer packaging material 2 is related to moisture adsorbed on the surface of the outer packaging material 2 on the inner space 3 side. That is, since the surface area with the larger surface roughness Ra has a larger actual surface area than the apparent surface area, the larger the surface roughness of the surface of the outer packaging material 2 on the inner space 3 side, the larger the surface roughness Ra is brought into the inner space of the vacuum heat insulating panel 10. This is because the amount of water increases. The reason why the surface roughness Ra is 0.2 μm or less will be described later.

  The manufacture of the vacuum heat insulating panel 10 in this embodiment includes a moisture removal process for removing moisture contained in the core material 1, a core material wrapping process for wrapping the core material 1 with the outer packaging material 2, and a welding process for welding the outer packaging material 2. And is mainly implemented in.

  In the moisture removal step, the core material 1 is heat-treated to remove moisture contained in the core material 1 until the moisture content is 0.05% by weight or less (preferably 0.02% by weight or less). The reason why the water content of the core material 1 is 0.05% by weight or less (preferably 0.02% by weight or less) will be described in detail later.

  In the core material wrapping step, after the moisture content of the core material 1 is equal to or less than the above value and the temperature of the core material 1 is lowered to a predetermined temperature, the core material 1 is placed on the concave side of the bulging portion 4 of the outer packaging plate 2B. And the peripheral edges of the two outer packaging plates 2A and 2B are aligned and overlapped. Thereby, it will be in the state where the core material 1 was wrapped with the outer cover board 2. FIG.

  The welding process will be described with reference to FIG. The welding process is performed in a first welding process performed in order to provide the opening 6 in a part of the peripheral edge of the outer packaging material 2 and in the first welding process in a vacuum while the internal space 3 is kept in a vacuum state. It is divided into the 2nd welding process performed in order to seal the opened part. The first welding process can be performed in the atmosphere.

  As a welding method, known welding methods such as seam welding, arc welding, laser welding, and electron beam welding can be used. However, when the outer cover plates 2A and 2B are thin stainless steel plates, it is preferable to use seam welding. This is because the outer cover plates 2A and 2B are thin stainless steel plates, and when the bulging portion is formed by drawing, wrinkles may occur in the peripheral portion, and the peripheral portion where the wrinkle is generated is joined by welding. This is because there is a high possibility of poor welding occurring in the gap between the two outer packaging plates 2A and 2B. Examples of poor welding include burn-off. Therefore, it is preferable to weld without a gap while crushing wrinkles by using seam welding that can be welded while applying pressure from above and below the outer packaging plates 2A and 2B.

Here, the procedure of performing the first welding process and the second welding process using seam welding will be described with reference to FIG.
Fig.2 (a) is explanatory drawing of a 1st welding process. The core material 1 is accommodated in the concave side of the bulging portion 4 of the outer cover plate 2B, and the outer cover plate 2A, 2B is aligned with the peripheral portions of the outer cover plates 2A and 2B, and the outer peripheral plate is seam welded. While pressing in the thickness direction, three sides (7a, 7b, 7c) of the four peripheral edges of the outer cover plate 2 are each linearly seam welded and sealed. As a result, one side of the peripheral portion remains as the opening 6. This first welding process can be performed in the atmosphere.

  The second welding process needs to be performed in a vacuum. This is because the internal space 3 is evacuated through the opening 6 to be in a vacuum state with a pressure of 1 Pa or less. Therefore, if a device in which a seam welding machine is installed in a vacuum chamber is prepared and the sealing portion 7d is formed by performing seam welding on the opening 6 in the vacuum in this device, the vacuum of the present invention is formed. Insulating panels can be manufactured.

<Reason why the water content of the core material is 0.05% by weight or less>
Next, the reason why the amount of water contained in the core material 1 is 0.05% by weight or less will be described.
FIG. 3 shows the results of investigating to what extent the amount of water contained in the core material 1 can be removed to maintain a certain degree of heat insulation performance. This figure shows a prototype of a number of vacuum insulation panels using core materials 1 made of a plurality of glass wools having different moisture contents, and three months after the thermal conductivity immediately after the trial and the temporal change in thermal conductivity almost stop. The result of investigating the thermal conductivity of is shown. When the upper limit of the allowable thermal conductivity is 5 mW / m · K, which is the average level of the thermal conductivity immediately after production of the high-performance vacuum heat insulating material generally used in the world, From this investigation result, it can be seen that those satisfying the thermal conductivity have a water content of about 0.05% by weight contained in the core material 1. A coulometric titration Karl Fischer moisture meter manufactured by Kyoto Electronics Industry Co., Ltd. was used to measure the amount of water contained in the core material 1.

  From this investigation result, it can be confirmed that the vacuum heat insulation panel 10 capable of maintaining good heat insulation performance for a long period of time can be manufactured by removing the moisture content of the core material 1 made of glass wool to 0.02% by weight. . In addition, although there is some change in the thermal conductivity over time, the upper limit is 0.05% by weight as the moisture content of the core material 1 that can be expected to eventually be kept below 5 mW / m · K. It can be seen that it is. Therefore, in the present embodiment, the water content of the core material 1 is set to 0.05% by weight or less (preferably 0.02% by weight or less).

Example 1
Hereinafter, specific examples of the vacuum heat insulation panel 10 will be described. Stainless steel foil (SUS304) having dimensions of 220 mm × 220 mm × thickness of 100 μm was used for the outer cover plates 2A and 2B constituting the outer cover material 2 for wrapping the core material 1. As the stainless steel foil (SUS304), five types having a surface roughness Ra of 0.05 μm, 0.10 μm, 0.20 μm, 0.30 μm, and 0.40 μm were prepared. In addition, one outer packaging plate 2B was provided with a bulging portion 4 having a size of 190 mm × 190 mm × height 5.0 mm by press forming.

For the core material 1, glass wool of about 1200 g / m ² was used. Then, this glass wool is inserted in an electric furnace in an air atmosphere in advance and subjected to a heat treatment at a temperature of 200 ° C. for 3 hours, and then taken out from the furnace and immediately put into a desiccator at room temperature (20 ° C.) and a relative humidity of 30%. The cooling process which moved and hold | maintained for 30 minutes was performed. The conditions for the heat treatment and the cooling treatment are conditions determined by conducting a preliminary experiment so that the amount of water contained in the core material 1 is 0.03 to 0.04% by weight.

  Thereafter, the core material 1 after the cooling treatment was taken out from the desiccator, and the outer packaging plate 2A, the core material 1, and the outer packaging plate 2B were superposed in this order. At this time, the core material 1 was accommodated so that the inside of the bulging part 4 provided in the outer packaging plate 2B could be filled without a gap. And the peripheral part of outer packaging board 2A and the peripheral part of outer packaging board 2B were welded and joined in the air | atmosphere by seam welding. In this seam welding, the seam welding was divided into three times along the outer periphery of the three sides of the rectangular outer cover plates 2A and 2B, and each was welded linearly, leaving the remaining one side as an opening.

  The seam welder used was a single-phase AC type, the upper electrode was a disk having a diameter of 100 mm and a thickness of 4 mm, and the curvature of the electrode tip was 20R. The lower electrode has a block shape with a thickness of 4 mm. Both the upper electrode and the lower electrode are made of chromium copper. The welding conditions were as follows: pressing force: 150 N, welding speed: 1 m / min, welding current: 1.6 kA, and the on / off ratio of the energization time was 3 ms / 2 ms.

  Next, the workpiece to be welded on the three sides and the seam welder were brought into the vacuum chamber, and the vacuum chamber was connected to a vacuum pump and evacuated until the pressure in the inner space of the outer cover plates 2A and 2B became 1 Pa or less. After that, the opening was welded and sealed in vacuum.

The thermal conductivity was evaluated as a performance evaluation of the manufactured vacuum insulation panel. The change over time in the thermal conductivity under the following environment was measured.
First, the thermal conductivity of the vacuum heat insulation panel immediately after manufacture was measured, and then the vacuum heat insulation panel was subjected to an environmental load test in which both a high temperature environment and a low temperature environment were repeated. Specifically, after holding the vacuum heat insulation panel for 12 hours in a temperature environment of 80 ° C., hold it for 12 hours in a temperature environment of −15 ° C., and then form a temperature cycle in which these temperature environments are alternately repeated every 12 hours. did. When this environmental load test was started and 60 days passed, the vacuum heat insulation panel was taken out and the thermal conductivity was measured. After the measurement of thermal conductivity, the environmental load test was continued again. Thereafter, the vacuum insulation panel was similarly taken out every 60 days, the thermal conductivity was measured, and the environmental load test was continued.

  Evaluation of thermal conductivity is performed using a thermal conductivity measuring device HC-074 / 200 manufactured by Eiko Seiki Co., Ltd. under the condition that the average temperature of the central portion of the vacuum heat insulating panel is 25 ° C., and the surface roughness Ra of the stainless steel foil is The thermal conductivity was measured for a plurality of different vacuum insulation panels. In detail, the average value was calculated | required about 3 vacuum heat insulation panels with the same surface roughness Ra of stainless steel foil, and it was set as the thermal conductivity for every surface roughness Ra of stainless steel foil.

  Table 1 shows the measurement results of the thermal conductivity immediately after the production of the vacuum heat insulation panel, at the time point of every 60 days of the environmental load test.

  From Table 1, it is clear that the smaller the surface roughness Ra of the stainless steel plate used for the outer packaging material, the smaller the increase in thermal conductivity even if the number of days has passed since the production. In particular, the 0.05 μm vacuum thermal insulation panel (shown as No. A in Table 1) having the smallest surface roughness Ra of the stainless steel plate has a thermal conductivity after 180 days as compared with the thermal conductivity immediately after production. However, the vacuum insulation panel was extremely excellent in terms of deterioration of heat insulation performance.

  The vacuum heat insulation panels other than the 0.05 μm vacuum heat insulation panel (shown as No. A in Table 1) having the smallest surface roughness Ra of the stainless steel plate have a thermal conductivity between immediately after production and after 180 days. Although an increase is observed, the heat conductivity of any vacuum insulation panel is greatly increased from immediately after manufacture until 60 days later, and the change thereafter is small and the heat conductivity is stable. This is because most of the moisture adsorbed on the surface of the stainless steel plate used for the outer packaging material immediately after production becomes gas molecules due to a rise in the temperature of the vacuum insulation panel. This is because it was released into the internal space.

  In addition, the increase in thermal conductivity is very small after 60 days after production. This is because the vacuum heat insulation panel of the present invention was joined by seam welding instead of using a heat seal for joining the peripheral portions of the outer packaging materials 2A and 2B, so that moisture did not enter the vacuum heat insulation panel from the peripheral portion. I understand. That is, the welded structure is effective for maintaining the heat insulating performance of the vacuum heat insulating panel over a long period of time.

  Furthermore, from the results shown in Table 1, the surface roughness Ra of the surface of the outer packaging material 2 on the inner space 3 side is an index of 0.2 μm or less considering that the change in thermal conductivity is small. .

  The vacuum heat insulation panel manufactured by implementing this invention is used suitably for electrical appliances, such as a vending machine of drinks, a heat exchanger, such as a refrigerator and a hot-water supply apparatus, an electric pot, and a copy machine.

DESCRIPTION OF SYMBOLS 1 Core material 2 Outer packaging material 3 Internal space 4 A bulging part 6 Opening part 10 Vacuum insulation panel

Claims (1)

A vacuum insulation panel in which a core material made of inorganic fibers is wrapped in a stainless steel outer packaging material, and the inner space of the outer packaging material in which the core material is wrapped is in a vacuum state,
The amount of water contained in the core material is 0.05% by weight or less,
The surface roughness Ra of the surface on the inner space side of the outer packaging material is 0.2 μm or less,
The pressure of the inner space of the outer packaging material enclosing the core material is 1 Pa or less,
A vacuum heat insulation panel for electrical equipment, characterized in that a peripheral portion of an outer packaging material is sealed by welding.

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